1. Field of the Invention
The present invention relates to a photoelectric conversion apparatus.
2. Description of the Related Art
In recent years, photoelectric conversion apparatuses, for example, a CCD image sensor and a CMOS image sensor have been used for an image read out apparatus such as a copy machine, and techniques for obtaining excellent images have been disclosed (see Japanese Patent Application Laid-Open No. 2006-211363, for example). Such a photoelectric conversion apparatus includes photoelectric conversion elements which convert a light signal into an electrical signal. For improved resolution of the photoelectric conversion apparatus, the sensitivity of the photoelectric conversion elements to a light signal needs to be increased. Also disclosed is a technique for reducing the number of wiring layers in an imaging region where photoelectric conversion elements are arranged, in order to increase the sensitivity of the photoelectric conversion elements (see Japanese Patent Application Laid-Open No. 2004-186407, for example).
In the technique disclosed in Japanese Patent Application Laid-Open No. 2006-211363, circuits for reading out signals are arranged between the photoelectric conversion elements. As a result, it is unfortunately difficult to reduce the number of wiring layers in the imaging region, while maintaining a sufficient area for the photoelectric conversion elements. In the technique disclosed in Japanese Patent Application Laid-Open No. 2004-186407, a metal wiring layer in the imaging region can be composed of only a single layer. However, transfer control signal lines for reading out electric charges accumulated in the photoelectric conversion elements, and reset control signal lines for resetting the electric charges accumulated in the photoelectric conversion elements have to be routed in a poly silicon layer. Unfortunately, such a configuration cannot accommodate a higher rate resulting from improved resolution of the photoelectric conversion apparatus.
The present invention has been made in the light of the above mentioned problems. The object of the present invention is to provide a photoelectric conversion apparatus in which a metal wiring layer can be composed of only a single wiring layer without a decrease in the read out rate.